Taking the Platymonas subcordiformis as sample and the Nd:YAP laser (1 341 nm)as the light source, the effects on chloroplast autofluorescence intensity and chloroplast area of Platymonas subcordiformis irradiated by laser were studied using confocal laser scanning microscopy. The autofluorescence images and fluorescence spectra of the Platymonas subcordiformis  irradiated by Nd:YAP laser were obtained by the excitation of 488 nm Ar⁺ laser. The results showed that all the laser irradiation dose, except the irradiation group with parameters of 10 W power and 60 s duration time, improved the autofluorescence intensity of Platymonas subcordiformis, and all the doses increased the chloroplast area. The laser can stimulate the chloroplast evelopment of Platymonas subcordiformis, promoted the growth of algal cells and improve the activity of chloroplast photosynthesis.